The genus Apoglossum J. Agardh has traditionally been placed in the tribe Delesserieae. Our morphological observations on Apoglossum and the "Delesseria" species belonging to the resurrected genus Paraglossum from the Southern Hemisphere show that they possess a distinct procarp. Apoglossum has two one-celled sterile groups that divide after fertilization and Paraglossum consists of two one-celled sterile groups that do not divide after fertilization, but in which the nuclei divide to produce four to eight nuclei in the undivided sterile groups. In contrast, the procarp in Delesseria sanguinea, the type species of the tribe Delesserieae, consists of two 2-6 celled sterile groups before fertilization and the number of sterile cells double after fertilization. The development of the carposporophyte in both Apoglossum and Paraglossum is shown to be unique in the subfamily Delesserioideae. The pit connections between the segments of the gonimoblast filaments broaden without fusion and secondary carposporangia are produced. This pattern is absent in other members of the Delesserioideae, but has been reported for the tribes Myriogrammeae and Schizoserideae in the new subfamily Phycodryoideae Lin, Fredericq et Hommersand. Based on both LSU rDNA and rbcL sequence analyses, the Delesserieae is restricted to species of Delesseria and Membranoptera from the North Atlantic and North Pacific Oceans. In contrast, the species of Apoglossum and Paraglossum form a distinct cluster having a center of distribution in the Southern Hemisphere with only a few species, such as Apoglossum ruscifolium, reaching the Northern Hemisphere. In this study, details of post-fertilization development leading to the cystocarp are illustrated for the type species of Apoglossum and Paraglossum and a new tribe, the Apoglosseae, is recognized in the Delesseriaceae.

Key words: Apoglosseae, Cystocarp, Delesseriaceae, Delesserioideae, Molecular, Rhodophyta